船舶结构动力学

第一章绪论一、现代结构动力学的研究内容1、外载荷分析确定性、周期性、瞬态：动力机械，旋转机械产生的激励碰撞、爆炸、冲击等瞬态荷载随机性：风荷载、波浪荷载、地震荷载、车辆等路面行驶引起的荷载2、结构系统的动力响应时域：载荷可以是非线性的，系统也可以是非线性的，解析解法，数值解法频域：目前仅能处理线性化系统，谱分析方法，优点：计算效率高时频混合分析方法：将时域解法与频域解法的优点结合，提高计算效率和求解精度解析法：数学上直接求解，许多实际结构难以采用该方法数值解法：工程上可以应用的近似解法，有限元法、边界元法、随机样条法、有限条法13、结构系统的辨识和参数估计动力学的拟问题（1）已知input和output，识别结构参数（2）已知input满足一定假设，output可测，识别结构参数（3）Healthmornitoring:a、有无结构失效

b、损伤位置

c、损伤程度SystemInputLoadsoutputResponse？InputLoadsoutputResponse24、容许标准和可靠性分析评估结构系统在某种载荷激励下的可靠性，系统寿命评估，系统疲劳分析等。5、结构振动控制大型结构如高层、潜艇、海洋平台等，环境荷载比较恶劣，在使用过程中会出现幅度比较大的振动。这些振动会诱发（1）疲劳破坏（2）降低系统的可靠度（3）给居住会作业人员带来身体不适措施：在结构上安装控制设备（装置），使结构具有自动调节的能力，从而使其振动减小，避免破坏。在建筑结构中主要是抵抗风、地震载荷、桥梁的振动上海电视塔、杨浦大桥等都安装了减振装置，日本的200多个高层建筑海洋结构主要抵抗波浪、风荷载控制方法主要有：被动式控制：调谐质量阻尼器，调谐液体阻尼器，粘弹性阻尼器等主动控制：主动质量驱动器等半主动控制：主动变刚度，主动变阻尼，磁流变阻尼器，电流变阻尼器混合式控制6、结构动力优化设计按照设计要求确定可控变量或设计变量使结构系统达到预期的状态，或者达到最优设计目标最优综合或最优设计3SpecialtopicI:Dynamicresponse

动态响应4567不同方法计算whipping响应的比较8Springinganalysis激励频率固有频率9Inwhippingandspringingthereare101112通过分析结构能量传递途径，采用改变结构参数实现抑制振动向目标区域传递1314结构破坏指数15冰载测量16171819202122结构动力学的前沿和热点问题主动控制技术海洋工程动力学海上陆色能源开发的动力学问题23IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)24SepecialtopicII:IMPULSIVEPRESSURELOADING

ANDRESPONSEASSESSMENT(V.7)

脉冲压力载荷与响应评估2425IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)Damaged

structureduetoBowSlamming艏部砰击下的结构损伤Damagedplate外板损伤Damagedstiffener骨材损伤INTRODUCTION2526IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)DamagedstructureduetoSternSlamming艉部砰击下的结构损伤Damagedplate外板损伤Damagedstiffener骨材损伤2627IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)DamagedstructureduetoSloshing晃荡引起的结构损伤DamagedcorrugationImpactedArea2728IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)DamagedstructureduetoGreenWater上浪引起的结构损伤DamagedwaterbreakerDamagedstiffener2829IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)Structuraldesignagainstimpulsivepressureloadingsfromslamming,sloshingandgreenwaterhasalwaysbeenadifficulttask.Manyshipshavestillreportedexperiencingstructuraldamageduetoimpulsivepressureloadings.Thisindicatesthattherelevantrulesofclassificationsocietiesneedstobeimprovedregardingimpulsivepressureloadings.

受脉冲压力载荷（砰击、晃荡、上浪等）作用的船体结构的设计总是一件棘手的事情。到目前为止，脉冲载荷引起的结构损坏还是时有发生，表明船级社现行的相关规范需要进一步改进。Whenthedurationofanimpulsivepressureloadingismuchshorterthanthenaturalperiodoftheimpactedstructure,theimpulsemayrepresenttheloading.However,ifthedurationislongenoughascomparedtothenaturalperiod,theamplitudeofpressuremayplayanimportantrole.当脉冲压力载荷的持续时间远远小于结构的固有周期时，可以用脉冲特性来描述载荷；当脉冲压力载荷的持续时间远远大于结构的固有周期时，可以用压力峰值来描述载荷。Inextremecases,thestructuraldesignagainstimpulsivepressureloadingsmaybetreatedasanultimatelimitstateoranaccidentlimitstateproblem.However,formoreprobablesituations,thiscanbesolvedasaserviceabilitylimitstateproblemespeciallyfromtheimpactsofslammingwherebythetolerableextentofdamageneedstobeprovided.在极端情况下，脉冲压力载荷作用下的结构设计可以用极限强度或事故强度问题处理。但在更多的情况下，可以将该问题当作服务强度来处理。

29Modelandfull-scaletest模型和实船试验技术

Modeltest

:模型试验

-droptestoncontainershipsternsection(Yang,etal,2007)集装箱船尾部剖面落体试验 -droptestonrigidanddeformablecone-shapedsamples(Peseux,etal,2005)刚性和弹性锥形体落体试验 -droptestonflatplate(HigoandYamada,2006)平板落体试验 -planningcraftmodelinobliquewaves(RosenandGarme,2004)滑行艇模型斜浪中试验

Fullscaletest:实船试验 -deep-Vpleasurecraft(CarreraandRizzo,2005)深V型游艇 -containershipintheNorthPacificOcean(Lee,etal,2007)北太平洋集装箱船试验30IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

LOCALSLAMMING30Numericalsimulation

数值模拟

-VOF(VolumeofFluid)andSPH(SmoothedParticleHydrodynamics) -explicitFEManalysisfor2Drigidwedge(Stenius,etal,2005)二维刚体显式有限元法 -directcouplingofFEMandWagnerrepresentationforelasticbody ofsmalldead-riseangle(Korobkin,etal,2006a)小斜升角问题的有限元与Wagner砰击压力直接耦合法 -numericalsimulationoftrappedaireffects(Dobashi,2006;2007)气垫效应数值模拟Analyticalprediction

解析计算

-publicationaboutanalyticalmethodshasbeenrareinrecentyears.很少 -analyticalsolutionfor2Dwedge(Yettou,etal.,2007)Yettou提出了一种新的解析算法31IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

LOCALSLAMMING31Practicalproceduresindeterminingdesignslammingpressure确定设计砰击压力的实用过程

-computationalprocedurefortheanalysisofaship’smotionsinwavesandspatialmeanslammingpressures(Ould,etal.,2005)波浪中船舶运动以及平均砰击压力空间分布的计算流程 -numericalproceduretopredictslammingloadson offshoresupplyvessel(Schellin,2006) carcarrier(HermundstadandMoan,2005) cruiseship(HermundstadandMoan,2007)海洋工程供应船、滚装船、游船的砰击载荷预报流程 -feed-forwardneuralnetworktopredict horizontalforce(Fullerton,etal.,2007) peakvalueofslammingpressure(ChenandXiao,2005)利用神经网络技术预报横向力和砰击压力峰值32IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

LOCALSLAMMING3233IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

LOCALSLAMMING局部砰击

Pressurecoefficientsobtainedusingacommercialpackage(Yang,etal.,2007)经典理论、经典模型试验、新模型试验、CFD计算的比较33Background背景

-Ingeneral,theglobalslammingresponseneedstobecombinedwiththesimultaneouslyobtainedglobalandlocalsteadystateloadeffects,intermsofextremevaluesforultimatelimitstatechecksandcyclicloadhistoriesforfatiguedesignchecks.总体砰击载荷响应一般与稳态波浪载荷相叠加，用于极限强度和疲劳强度校核 -Generally,3Deffectscanreducethe2Dslammingpressureforcebyapproximately30%.Fully3Dslammingpredictionmethodsarenotreadyforuseinaglobalresponseanalysis.Correctionfactorson2Destimatesmaybeappliedtoyieldreasonablevaluesfordesign.计入三维效应可以减小30%的砰击力，但三维砰击理论尚不成熟。34IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

GLOBALSLAMMINGMeasuredandcalculatedplammingpressure34GlobalStructuralModeling总体结构模型

-ThehullmaybemodelledbythebeamtheoryorFEshellmodels.Whileverticalbendingisrelativelywellrepresentedbybeamelements,modellingoftorsionalbehaviourofopenshipssuchascontainervesselsaswellascatamaransismorechallenging.船体结构可用梁理论或有限元模型进行分析；垂向弯曲问题可用梁理论较好的表示，但大开口船的扭转问题和双体船则比较麻烦 -Quiteaccurateresultsareobtainedifthebeammodelisbasedonanadvancedthin-walledgirdertheory.AmoredetailedFEmodelwillbenecessaryifthe1Dbeamistobeappliedinthedynamicanalysis,toobtainresponsevaluesespeciallyforfatiguedesign.利用先进的薄壁梁理论可以较准确的结果；对于疲劳等问题，有限元方法比一维梁理论更好 -Nopublicationsseemtohavebeenpublishedonslamminginducedtorsionalresponseofships.砰击引起的扭转振动问题目前未见有文章发表。

35IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

GLOBALSLAMMING总体砰击

35WhippingAnalysis:Extremevaluesforultimatestrengthdesign颤振分析：极限强度设计

-experimentontheshort-termprobabilitydistributionofthemidshipsverticalhoggingbendingmoment(DrummenandMoan,2007)通过模型试验确定载荷的短期概率分布 -numericalandexperimentalstudytomeasureshipresponsestoextremewaveimpact.数值和试验研究极限砰击下的船体响应

(Minamietal.,2006) -hybridmethodforcalculatingwave-inducedlinearandnonlineargloballoadeffectsinshipswithhullflexibility(WuandMoan,2005)线性与非线性混合法 -experimentalandnumericalinvestigationoftheeffectofbowflareandsternslamminginducedwhippinginlargepassengervessels(Cusanoetal,2007)大型游船艏艉砰击下颤振响应的模型与数值研究 -experimentontheVBMresponsetosternslammingloadsonalargemodernpassengership(Dessietal.,2007)大型豪华游船艉砰击 -long-termanalysisofextremesloshingandwhipping-inducedpressuresandstructuralresponseoftheMarkIIIcontainmentsystemforLNG (Graczyketal,2007)MarkIII型大型LNG船围护系统极端晃荡和颤振压力长期预报和结构响应36IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

GLOBALSLAMMING总体砰击

36WhippingAnalysis:Cyclicstresshistoryforfatigueanalysis颤振响应，疲劳分析中的循环载荷

-Fullscalemeasurements:实船试验

Capesizeironorecarriers(Moeetal(2005)andStorhaugetal(2006))矿砂船 4000TEUcontainership(Drummenetal,2006,2007)集装箱船 10000dwt.generalcargoship(AalbertsandNieuwenhuijs,2006)一般货船 6800TEUcontainership(Toyodaetal.,2006) -Forcontainerships,thepredictedtotalfatiguedamageforthemidshipssectionwasapproximately50%higherthanthedamagedeterminedexperimentally.对集装箱船，理论预报的疲劳损伤比试验值大50%左右 -Highfrequencydamagecanbesignificantlyreducedbyincludingthesteadywavefortherelevantship.当包含稳态载荷引起的破坏时，高频疲劳损伤的程度相对明显减轻。37IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

GLOBALSLAMMING总体砰击

3738IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

SLOSHING晃荡

Sloshingtestequipments试验装置Modelandfull-scaletests模型和实船试验forquasifullscalemodel准实船for“intermediate”scalemodel中模型forsmallscalemodel小模型38Modelandfull-scaletests模型和实船试验

-Smallscalemodeltestsgiveareasonableoverviewoftheoverallsloshingmotionsinsidethetankbutthelocalpressuresmeasurementsarestilldifficulttoobtainduetothehighlylocalized(intimeandspace)pressureswhichoccurduringimpact.Theproblemoftransferringthesepressurestoafullscalerepresentsabigchallenge.小模型可获得晃荡运动整体特征，但由于砰击压力在时间和空间上的特征，测量困难，转换成实船更难 -Importantdatabasesofthequasifullscalemeasurementswererealizedusingthesetestsinvariousresearchprojects,butmanyproblemswerereportedwithrespecttotherepeatabilityofthemeasurementthatmakestheproperinterpretationanduseoftheresultsverydifficult.在不同的项目中，准实船试验积累了很多数据，但结果离散性问题使利用和解释这些结果变得困难 -“Intermediate”modeltestswillallowforthedetailedvalidationofthesimplifiedsemianalyticalandmoresophisticatednumericalmodels.Indeed,alltheimportantimpactparameterscanbemeasuredwithverygoodprecisionandthisallowsforpropervalidationofalltheintermediatemodellingsteps.中模型试验可以为简化的半解析预报方法和复杂的数值计算模型提供详细的验证39IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

SLOSHING 晃荡

39Numericalmodellingofhydro-structureinteractionsduringimpacts砰击中流固耦合的数值模拟

-Evenifsomeattemptsweremadetosolvethe3Dimpactproblems,the2Dmodellingoffluidflowisusedmostoften.Onthestructuralsidethe3DeffectsoftheresponsecanbetreatedbythestandardFEMcodes

二维流动模型比三维模型更常用，结构的三维效应用有限元模拟CFDNumericalsimulationsCFD数值模拟

-themostpopularmethodsbelongtothefamilyoftheVOF(VolumeofFluid)techniqueandtothesocalledSPH(SmoothedParticleHydrodynamics)method.However,allCFDmethodssufferfromvariousnumericalproblemswhenitcomestotheevaluationofhighlylocalizedpressures.VOF和SPH法最常用，但当涉及到砰击压力时，所有的数值方法都存在问题40IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

SLOSHING 晃荡 V.7Typicalsloshingmotionssimulated40

41IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

SLOSHING 晃荡

Comparisonofthequasi-staticandhydroelasticstructuralresponses准静态和水弹性结构响应41Combinedsemianalytical(fluidflow)andfiniteelement(structure)models半解析（流体）和有限元方法的组合

-Semianalyticalimpactmodelsrepresentanothertypeofmethodforsloshingimpactproblems.Theideaistoidentifythemosttypicalimpactsituationsandthensimplifytheminordertobeabletodescribethemwithsimplegeometryincludingthefewmostimportantphysicalparameters.半解析砰击模型是晃荡砰击的另一类解法，找出最典型的砰击，通过简化，以几个简单但重要的物理参数去描述砰击42IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

SLOSHING 晃荡

Aeratedimpactandcorrespondingsimplification(left-realsituation,middle-geometricalsimplification,right-mathematicalmodel42Experimentalinvestigations试验研究-Anonintrusivequantitativevelocitymeasurementtechnique,PIV(ParticleImageVelocimetry)andBIV(BubbleImpactVelocimerty),highlightedturbulenceintensitythroughoutthedifferentphasesoftheimpingement-runup-overtoppingsequence. ThisscenariosuggestedtheapplicationofRitter’sdam-breakingflowsolutiontogreenwaterproblem.PIV测量上浪瞬态速度场，BIV测量平均速度场，溃坝理论的实用性43IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

GREENWATER上浪

.

InstantaneousvelocityfieldusingPIVandmeasuredmeanvelocityfieldusingBIV(Ryuetal,2007a)43Experimentalinvestigations试验研究-ThemodeltesttosimulatethegreenwaterscenariosforafixedFPSOindicatedthattheplungingwaveplusthedam-breakingtypeeventasthemostcommonwater-ondeckscenario,whereastheso-calledhammer-fisttypewasfoundtobethemostdangerousone.44IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

GREENWATER上浪

Hammer-fisttypeevent:evolutionoftheshippedwater(Grecoetal,2007)44Numericalsimulations数值模拟

-Impactingflowfeatures:Domaindecompositiontechnique(Navier-Stokessolverwithalevelset(LS0techniqueandBEMsolver)(Grecoetal,2007)-Dambreakingproblem:Volume-of-fluid(VOF)scheme(Kleefsmanetal,2005),VOFtechniquewithafinitevolumemethod(Zhangetal,2005)andEdge-basedstabilizedfiniteelementsolverusingVOFextensions(EliasandCoutinho,2007)-Two-layerflowovertoppingafixedbodywithaverticalwall:Modifiedmarkerabdcell(MAC)method(Yamasakietal,2005)-Freesurfaceoverfixeddeckwitharoundprofile:movingparticlemethod(ShibataandKoshizuka,2007)-Watershippingproblem:smoothedparticlehydrodynamics(SPH)method(VioleauandIssa,2007)45IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

GREENWATER上浪

Two-layerflowovertoppingafixedbodywithaverticalwall:Modifiedmarkerandcell(MAC)method(Yamasakietal,2005)45Loadalleviation

-PhamandVaryani(2006)comparedtheperformancesofV-shapeandvanetypebreakwatersfordifferentvaluesofthegeometricalparameters.TheyconcludedthattheconfrontinganglehaslessinfluenceinbothcasesforloadalleviationandthattheV-shapebreakwaterismoreeffectiveinsustainingpartofthewaterflowotherwisefullydirectedtowardcontainersandstructuresplacedbehind.挡浪板的效果46IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

GREENWATER上浪

46Experimentalandnumericalsimulation试验和数值模拟

-Theenergyoftheexplosiveisconsumedbytheshockwavesandagasbubbleandapproximately,60%intoshockwaveand40%tothegasbubbles.

爆炸能量的60%转换成冲击波，40%为气泡

-Sturtevant(2007)describedthefullshipshocktrials(FSST)donebyUSNavy.ThecurrentFSSTpracticeconsistsofthreeUNDEXshotsof10,000poundHBXexplosivechargeweightdetonatedinseriesatlargestand-offdistancesabeamoftheship.Thecostsassociatedwiththetestcanexceed$50millionpertrial.美国海军实船试验，每个试验花费5000万美元

-Bubblecollapseunderasubmergedflatplate:RANSE(Reynolds-averagedNavier-Stokesequations)basedfinitedifferenceEquationIndependentTransientAnalysisComputerCode(Kanetal,2005)浸没平板下的气泡溃灭数值计算

-Shocktransparency:basiclinearmethod(Iakovlev,2006;2007)

冲击波透射：基本线性法47IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

UNDERWATEREXPLOSION水下爆炸Fullshipshocktrial(FSST)(Sturtevant,2007)47Experimentalandnumericalsimulation数值与模型试验

-Effectofbulkcavitationandattenuationoffloatingstructuresresponse:ExplicitfiniteelementapproachwithBEM(Gong,2006) -Nearcontactcalculations:Thechinooksolverwiththelargedeformationfluid-structureinteraction(Gregson,2006) -Hullwhippingresponse:Thesource-sinkmethod(Noma,2006) -Ultimatestrengthofhullgirder:ExplicitFEMforbendingmoment,BEMforlocalpressurefrombubblejetandFEMforlocalstructuraldamage(Yasuda,2006;2005) -Explosionbubble:BEMcoupledwithstructuralFEcode(Klaseboer,2005)

Classificationsocietyrules船级社规范

-Lloyd’sRegisterRulesandRegulations(2008)describehowaship’sstructureisdesignedbytakingUNDEXintoaccount.Italsogivesgeneralinformationaboutshockwaves,bubblepulses,bubblejetsandtheireffectstostructuralresponse.Lloyd’sdefinesthreelevelsofshocknotationsfortheeffectsofaninitialshockwave.Inadditiontotheshocknotations,itdefinesdesignlevelsforwhippinginducedbyexplosionbubbleeffectsandanothernotationsforresidualstrengthassessment.英国劳氏规范（2008）有水下爆炸问题的较多规定和方法48IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)IMPULSIVEPRESSURELOADING:

UNDERWATEREXPLOSION水下爆炸

4849IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)

Cumulativeeffectofmultipleimpacts

多次冲击变形累积DAMAGETOSTRUCTURESAND

THEIRRESIDUALSTRENGTH 结构破坏和剩余强度

Deformedshapeofstiffenedplate

加筋板变形EffectsofmultipleimpactsandTrippingofstiffener

(a)P=0.631MPa

(b)P=1.656MPa

(c)P=2.070MPa

49COMPARISONOF

CLASSIFICATIONSOCIETIESRULES 规范比较

ShipType;OILTANKER withD.W.39,000TonLBP;172.mBreadth(mld.);31.40mDraft(Scantling,mld.);10.95mBlockCoefficient;0.785DesignSpeed;14.5knot油船底部砰击压力下板厚沿船长分布要求（四个规范）50IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)Requiredthicknessofthebottomplatebythebottomslammingpressure50ShipType;OILTANKER withD.W.39,000TonLBP;172.mBreadth(mld.);31.40mDraft(Scantling,mld.);10.95mBlockCoefficient;0.785DesignSpeed;14.5knot油船艏外飘砰击压力下板厚沿高度分布要求（四个规范）51IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)Requiredthicknessofsideshellplatebybowflareslammingpressure5152IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)H(TankHeight)=15.1mLc(Longitudinaldistanceofthetank)=17.40mbc(Transversedistance

ofthetank)=24.94mh(FillingHeight)=10.57m(0.7H)Calculatedpoint=10.57m(0.7H)油船晃荡砰击压力下的板厚比较（横舱壁，纵舱壁）CalculatedpointClassAClassBClassCCSRTransverseBulkhead9.508.936.516.35LongitudinalBulkhead9.5010.958.608.60Requiredplatethicknessbysloshingpressure(mm)5253IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)Requiredthicknessofthedeckplatebygreenwaterloads上浪砰击下的甲板厚度要求53Impulsivepressureloadsgeneral

Eventhoughsignificantprogresshasbeenmadeoverthelastdecade,theproperdeterminationofrelativeimpactgeometry,relativevelocityandamountofentrappedairstillremainsextremelychallenging,sincetheoverallsea-keepingproblemofshipsailingwitharbitraryforwardspeedinwavesisstillanopenproblem.由于船舶航行条件的复杂性，砰击过程中的相对砰击面、速度、气垫等的确定仍然存在困难Localslamming

Numericalpredictionsofslammingpressuresaccountingforviscousflowseparation,entrappedair,compressionoffluidsandelasticityofstructuresneedtoenhancetheiraccuracy,stabilityandefficiency.Morevalidationswithtestsresultsareneededfortheapplicationofthesemethodsindesignpractice.对局部砰击，数值计算方法的精度、稳定性和计算效率需要进一步提高，为提高这些计算方法的实用性，试验验证工作需要加强

54IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)54Globalslamming

Generally,3Deffectscanreducethe2Dslammingpressureforcesignificantly.Fully3Dslammingpredictionmethodsarenotreadyforuse.Correctionfactorson2Destimatesmaybeappliedtoyieldreasonablevaluesfordesign.

Thecontributionfromvibratoryresponsemaydoublethefatiguedamageinducedbywave-frequencyloads.Thedampingmayplayanimportantroleinnumericalanalysisandmeasurements.Therefore,itisimportanttocontrolthedampinginmodelteststocorrespondtothatforrealships.对总体砰击，计入三维效应可明显降低二维砰击载荷，但三维计算方法还不成熟，二维方法加三维修正可以得到更合理的设计值高频振动响应引起的疲劳损伤可与波频载荷相当，其中阻尼的作用很大，因此在模型试验中考虑阻尼与实船的相似性很重要。55IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)RECOMMENDATIONSFOR

STRUCTURALDESIGNGUIDANCE结构设计指导性意见V.755Sloshing

TheFroudescalinglaw,whichisusuallyappliedforsmallscalemodeltests,yieldsconservativevaluesformaximumpressure.However,thetimeisalsodifferentlyscaledbyvariousscalinglaws.Therefore,theeffectofscalingthepressuretimehistoriesmayonlybeassessedbyanalyzingthedynamicresponseofthecontainmentsystem.

Inspiteoftheeffortstoproperlysolvethesloshingimpactissues,manykindofuncertaintiesstillpersist.ThefullscalemonitoringoftherealLNGshipsundernormaloperationwouldcertainlybeveryhelpfulbutitseemstobeverydifficulttoperform.对于晃荡，按Froude相似率进行模型试验将使最大压力幅值偏大。LNG船的实船试验十分重要但也十分困难。56IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)56Greenwater

Forwatershippingproblems,abenchmarkingsystemwouldbeappreciabletocomparebothaccuracyandcomputationalcosts.Inthisperspective,thedam-breakproblemseemstobetheobviouscandidatetoprovideasharedsetofdata.

Iftheultimateobjectiveistoprovideloadstobeappliedtotheshipsuper-structures,themeasurementofgloballoadsonflexibledecks,aswellaswalls,shouldbesuccessfullyexploitedtofacilitatethecomparisonbetweensimulationsandexperiments.

对于上浪，计算精度和效率的相互比较验证很有意义，溃坝问题是个很好的比较对象。

57IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)RECOMMENDATIONSFOR

STRUCTURALDESIGNGUIDANCE

结构设计指导性意见57Impulseshape

Theeffectsofthetailpartontheextentofdamageisverysmallandthepeakpressureandthepeakwidtharetwomostinfluentialparameters.Unfortunately,mostoftheexperimentalortheoreticalinvestigationsreportedarefocusedonhowtoaccuratelypredictthepeakpressurebutthoseonthepeakwidthareveryfew.砰击峰值和持续时间对结构损坏很重要。58IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)Idealisedimpulsivepressurehistory58Multipleimpacts

Eveninasinglestorm,shellplatesofshipscanbeimpactedseveraltimes.However,theextentofdamagecanbeaccumulatedbymultipleapplicationsofimpact.Theeffectsofmultipleimpactsontheextentsofdamagehavenotyetbeenconsideredinanyclassificationsocietiesrules. Accordingtosomeexperimentalandnumericalinvestigationresults,theincreasedextentofdamageofplatesduetomultipleimpactscanbeapproximately50%.

多次砰击造成的结构累积损坏问题尚未得到重视Torsinalstrengthofstiffener

Thetorsionaldeformationsofstiffenersof damagedpartshavebeenclearlyseen. Therefore,anycriteriashouldbeprovided withwhichtorsionalstrengthofthestiffener canbechecked.Deploymentofadditional trippingbracketsintheregioncanbe apracticalmeasurewhereimpulsiveloadings areexpected.纵骨扭转强度问题应该引起重视

59IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)Deploymentexampleoftrippingbrackets59Allowableextentofdamage

Avoidingdamageduetoimpulsivepressureloadingsdoesnotseempractical.Therefore,specifyingtheallowableextentofdamageduetoimpulsivepressureloadingsseemsnecessaryformorerationalandpracticalstructuraldesign.Whendeterminingtheallowableextentofdamage,someoptimisationproceduresneedtobeinvokedconsideringtheinitialconstructioncosts,operationalexpensesanddirectandindirectrepaircosts.完全避免结构在脉冲压力下的损坏无法实现，应该提出许用损坏概念Reverseengineeringofdamagerecords

Whenpredictingtheimpulsivepressureloadingsinducedbyimpulsivepressureloadings,therearestillintolerableuncertaintieswhichexisteventhoughvariousresearchmethodshavebeenperformedtoimprovetheaccuracyofassessments.Theactualdamagerecordsmayunveilvaluableinformationwhichcouldhelpimproverelatedtechnologiesandpredictionaccuracyaccordingly.

实船损坏记录对改进预报方法和结构设计十分重要60IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)60Localslamming

Modelorfull-scaletestsarestillthemostreliableapproachinobtainingthepressuredistributionandforceontemporalandspatialscales.However,duetothecomplexityoftheslammingphenomenon,practicalmethodstoobtainrationaldesignpressures,forcesandstructuraldynamicresponsesforanewdesignisstillrequired.对局部砰击，模型和实船试验仍是最可靠的手段Globalslamming

The3Dcharacterofthebowandbulbofcontainershipsisparticularlychallengingtomodel.Themainchallengeinestimatingglobalslammingresponseisthecalculationoftheslammingforce,especiallyinobliqueseasduetotheeffectsofrollingmotion.

Thehighfrequencyfatiguedamageduetowhippingcanbesignificantlyreducedbyincludingthesteadywavefortherelevantvessel.Therefore,moreworkneedstobedonetoimprovethehighfrequencystressmodeling,whichincludesidentifyingandquantifyingthesourcesofdampingofthevibrationaswellasverificationoftheexcitationsourcesofhighfrequencyresponse.对于总体砰击，斜浪中的砰击问题、三维砰击问题仍然困难；高频振动阻尼和激励源确定很重要。61IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)CONCLUSIONS结论61Sloshing

Whenanalysingsloshingimpacts,thestructuralresponseshouldbetakenintoaccount.Animportantconsiderationisthetimescaleofaparticularhydrodynamiceffectrelativetowetnaturalperiodsforstructuralmodescontributingsignificantlytolargestructuralstresses.Morestructuralmodesmaybeincludedformembranestructuresanalysesthanforsteelstructures.

Thequasifullscalemodeltestsandintermediatescalemodeltestsarebelievedtobringmorelightintothisdifficultproblem.Severalexperimentalcampaignsarenowunderway,butstillnoclearandreliableresultshavebeenpublished.对于晃荡，分析中必须计入结构响应，特别是当水动力时间特征和湿结构的固有频率相近时62IMPULSIVEPRESSURELOADINGANDRESPONSEASSESSMENT(V.7)62Greenwater

Differentmeasurescanbeinvestigatedtoreducetheeffectsofgreenwateronthedeck.Forwardprotectionmaybeachievedintheformofforecastleandbreakwater,sideprotectionbymeansofwalls,ingeneralstructuralb